Introduction to Molten Salt Reactors


Molten salt reactor coolant flow diagram for loop type reactor [1].

Molten salt reactors (MSRs) are advanced reactor concepts that use liquid halide salt coolants to remove heat from the reactor core for use in energy generation or chemical processing. Molten salts are very chemically stable at high temperatures and under irradiation.

Eutectic LiF-BeF2 (66-33 mol.%) at 600 ˚C [2].


They flow much like water and operate at temperatures greater than 300 degrees hotter than commercial primary reactor coolants. They provide key benefits, including, (i) high degree of passive safety, (ii) atmospheric pressure operation, (iii) high thermal efficiency, and (iv) potentially a lower spent fuel per unit energy [3]. These advantages were demonstrated by the Molten Salt Reactor Experiment (MSRE) as well as other projects at Oak Ridge National Laboratory in the 1960s and 70s [4]. In 2001, the Generation IV International Forum, supported by the U.S. Department of Energy, selected MSRs as one of several concepts for deployment between 2010 and 2030 with the criteria of being clean, safe and cost-effective means of meeting increased energy demands on a sustainable basis [5]. A handful of private companies and universities work to design and build a commercial MSR in the USA [6].


A critical step towards the successful deployment of MSRs is the mitigation of corrosion of structural materials by liquid salts. This research group is engaged in experimental research of salt chemistry and materials compatibility. Our objective is to develop strategies to assure good long-term structural materials behavior in MSRs.

SEM images of the surface of the 316 stainless steel sample after exposure to molten LiF-BeF2 in a graphite capsule for 3000 hours at 700 ˚C [7].

[1] D. Holcomb, “Module 1: History, Background, and Current MSR Developments.,” 07-Nov-2017.

[2] B. C. Kelleher, “Purification and Chemical Control of Molten Li2-BeF4 for a Fluoride Salt Cooled Reactor,” PhD, University of Wisconsin – Madison, 2015.

[3] C. W. Forsberg, “Molten-Salt-Cooled Advanced High-Temperature Reactor for Production of Hydrogen and Electricity,” Nuclear Technology, vol. 144, no. 3, 2003.

[4] “A look back at the Molten Salt Reactor Experiment | ORNL.” [Online]. Available: [Accessed: 13-Jun-2019].

[5] “Generation IV Nuclear Reactors,” World Nucl. Assoc., Dec. 2017.

[6] “The Advanced Nuclear Industry,” 15-Jun-2015. [Online]. Available: [Accessed: 17-Mar-2018].

[7] G. Zheng, B. Kelleher, G. Cao, M. Anderson, T. Allen, and K. Sridharan, “Corrosion of 316 Stainless Steel in High Temperature Molten Li2BeF4 (FliBe) Salt,” J. Nucl. Mater., vol. 461, pp. 143–150, Mar. 2015.